Differentiation antigens on normal and Abelson virus transformed lymphocytes

Rabbit antisera to Abelson leukemia virus (A-MuLV)-induced murine lymphomas have been analyzed by absorption with a variety of murine lymphoma lines. Antibody binding to a panel of cell lines and normal lymphocytes was visualized by using hapten-sandwich indirect membrane immunofluorescence. Novel membrane antigens thereby detected are shared between lymphosarcomas, B lymphomas, normal B lymphocytes, and normal membrane immunoglobulin negative (sIg-) bone marrow cells, but are not found on T cells, thymic lymphomas, plasmacytoid lymphomas, or myelomas. The existence of such shared differentiation antigens suggests that sIg- A-MuLV-induced lymphosarcomas may be transformed B cell precursors. Since differences in the expression of these antigens on individual plasma-cytoid lymphoma lines were found, this category of lymphomas may include cells at a variety of differentiation states.

The differentiation of cytotoxic T cells in vitro. I. Amplifying factor(s) in the primary response is Lyt 1 + cell dependent

Within 15 hr of establishment of a murine mixed lymphocyte culture, a soluble mediator was produced that was capable of augmenting primary cytotoxic responses to alloantigen. The factor did not induce responsiveness in the absence of antigen, since the amplified response seen in its presence was specific for the stimulating alloantigen. The factor did not therefore appear to function by polyclonal activation of cytotoxic precursor cells. Production of the amplifying factor(s) was induced by unfractionated spleen cells, but not by cells subjected to UV irradiation or to sonication, making it likely that this deficiency is the basis of the well-documented failure of these stimulator cells to induce primary cytotoxic responses. The amplifying effects of the factor were distinctive from, but synergistic with, those of 2-mercaptoethanol. Production of the amplifying mediator did not require cell division but was dependent upon the presence of Lyt 1 + cells. On the other hand, Lyt 2 + cells were not needed for mediator production, but served as target cell population on which the factor exerted its action. These findings are compatible with the hypothesis that direct T-T cell collaboration can amplify the differentiation of cytotoxic cells.

Lymphocyte traffic within the bone marrow and selective retention of alloreactive cells

Earlier studies showed that large numbers of isotopically labelled thoracic duct lymphocytes (TDLs) enter the bone marrow (BM) within hours of injection but depart equally as rapidly by 12 to 24 hr. The significance of this rapid flux was investigated further. Early (1/2 to 2 hr) after the i.v. injection of TDLs, BM was shown to contain T cells capable of initiating a graft-versus-host (GVH) reaction in F1 hybrids and in other experiments memory cells against human serum albumin (HSA). Both GVH and memory cell activity had markedly declined in the BM by 12 hr. In contrast to the rapid departure of TDLs from syngeneic BM, F1 hybrid BM retained parental lymphocytes with GVH activity for alloantigens of the opposite parent. F1 hybrid BM under these circumstances supported the transformation and proliferation of lymphocytes activated in situ by alloantigens. These selectively retained T cells also reacted to third-party alloantigens. In addition, TDLs with memory for HSA were retained in the BM of F1 hybrids. The BM is a site in which alloreactive immune responses may be initiated or sustained.

Immunosuppressive ALS. II. Antibody to Ia antigens in heterologous anti-lymphocyte serum

The relationship between Ia alloantigens and xenoantigens detected by immunosuppressive heterologous anti-lymphocyte sera has been investigated. Three rabbit anti-rat lymphocyte sera were examined for the presence of antibodies to Ia antigens. Two of these sera, an anti-thymus membrane and anti-lymphocyte sera detected labelled cell-surface Ia antigens (mol. wt 35,000 and 27,000) present on rat spleen B cells. The third antiserum, prepared against fractionated soluble lymphocyte antigens, was essentially non-reactive with these antigens. Of these three heterologous antisera, the anti-membrane serum reacted with the same antigens detected by two alloantisera. It seemed possible that such an antiserum could modify a recipient animal's immune response in vivo in a fashion identical to alloantibody to Ia antigens. In fact, all three heterologous antisera, including one devoid of antibody to Ia proved immunosuppressive in vivo. These results suggest that antibodies to antigens other than Ia can induce prolonged allograft survival. Since heterologous sera bind Ia antigens, it remains to be determined whether monospecific heterologous antisera to Ia antigens can allograft survival. The results raise the prospect that more than one antibody specificity may contribute to the immunosuppression achieved with ALS.

[Effect of methotrexate on the expression of alloantigens in the population of murine lymph node cells]

The effect of methotrexate given intraperitoneally to (CBA X C57BL/6j) F1 mice on the expression of alloantigens in the lymphatic node cell population was investigated. For this purpose cells from intact or methotrexate-treated F1 mice were injected into the foot-pad of CBA mice. The reaction was estimated as an increase of the regional popliteal lymphatic node in comparison with contralateral (intact) one. The injection of methotrexate in doses of 50 and 75 mg/kg significantly increased the alloantigenicity of the F1 mouse lymphatic node cell population.

Mechanisms of clonal abortion tolerogenesis. II. Clonal behaviour of immature B cells following exposure to anti-mu chain antibody

This paper uses B-lymphocyte cloning methods to quantify the effects of anti-mu chain antibody on immature and mature B cells. Nude mouse spleen lymphocytes were incubated with various concentrations of sheep anti-mouse mu chain antibody for times varying from 10 min to 24 h. They were then washed and plated in the agar B-cell colony formation assay. Five to six days later, control B cells had developed into colonies with a plating efficiency of about 5%. B cells from newborn mice pretreated with anti-mu yielded fewer colonies. Remarkably low concentrations sufficed to inhibit subsequent mitogenesis. For example, 3 microgram/ml acting for 1 h or 0.1 microgram/ml acting for 24 h gave greater than 50% inhibition. Adult B cells were about thirty-fold more resistant to negative signalling. Immature cells become more profoundly inhibited as anti-mu treatment was prolonged. Anti-Ia or anti-H2 antibodies, in the absence of complement, did not deliver a negative signal. Anti-mu pretreatment also reduced the capacity of immature B cells to form clones of anti-hapten antibody-forming cells in a liquid microculture system where the triggering stimulus was a T-cell independent antigen. Mature 'T-independent' B cells were not inhibited. Populations of hapten-specific B cells prepared by the hapten-gelatin method were investigated in the agar cloning system. Pretreatment of immature cells with anti-mu reduced their capacity to form colonies, this subpopulation of cells behaving like unfractionated B cells. Furthermore, hapten-HGG delivered a negative signal also. Mature hapten-specific cells or unfractionated immature spleen cells formed normal numbers of colonies following hapten-HGG treatment. Overall, the studies support the view that anti-mu antibody and hapten-HGG deliver strong negative signals to immature but not mature cells with appropriate receptors. The value of anti-mu as a model, universal tolerogen was supported. Fluorescence-activated cell sorter (FACS) analysis was performed to study the relationships between functional inhibition and Ig receptor modulation. We confirmed that the IgM receptors of immature B cells are more readily modulated by anti-mu antibody than those of mature cells. Furthermore, the receptor regeneration could be partially inhibited amongst immature but not mature B cells. There was not a close quantitative relationship between the degree of modulation and the degree of functional inhibition. The results did not support the view that irreversible receptor modulation as such was the cause of functional inhibition.

Virus plaque assay: effective detection of virus plaque forming cells at the early stage of lymphocyte activation by mitogen and alloantigen

Activated lymphocytes were detected quantitatively by virus plaque assay (VPA) during the course of lymphocyte cultures stimulated by mitogen or alloantigen. In Con A-stimulated cultures, the number of virus-plaque forming cells (V--PFC) was a more sensitive method of detecting the early stage of lymphocyte activation than [3H]-thymidine (3H-TdR) incorporation. This evidence was obtained by two methods of collecting cells of each stage. First, when Con A-activated lymphocytes were fractionated by velocity sedimentation at unit gravity to separate cell populations according to each cell stage, the ratio of the number of V-PFC to the radioactivity of incorporated [3H]-TdR was larger in the earlier stage of cell cycle than in the later stage. Second, when cultured lymphocytes were synchronized directly by addition of excess thymidine and colchicine, similar results were obtained. In primary mixed lymphocyte cultures, the generation of cytotoxic lymphocytes (CTL) was correlated better with the proliferative response than with V-PFC production. It was also found that both the incorporation of [3H]-TdR and the generation of CTL were abrogated by cytosine arabinoside (Ara-C) added to cultures up to one day before assay, whilst the generation of V-PFC was not so markedly affected by Ara-C. These findings suggest that V-PFC represent the number of precursor cells which require one or more generations to differentiate to CTL and not simply the number of effector lymphoyctes already exhibiting cytotoxicity.

Modulation of Fc receptors on human peripheral blood lymphocytes by antisera against beta 2 microglobulin, Ia or immunoglobulin

The association between Fc receptors and other surface molecules was examined by EA-rosette (EAR) inhibition experiments. Twenty to 30% EAR were detected in suspensions of peripheral blood lymphocytes from normal individuals. Anti-β₂ microglobulin (βMi) sera fully suppressed EAR whereas anti-Ig, anti-Ia sera and heat aggregated IgG inhibited only 50–60% EAR. Thus almost half of the detected EAR were apparently not surface Ig positive B cells. Rabbit and monkey anti-βMi sera suppressed EAR effectively whereas rat and chicken antisera, despite strong βMi binding capacity, inhibited EAR poorly. The latter result was ascribed on the basis of immunofluorescent analysis to inadequate capping of βMi. Incubation of PBL with whole antisera suppressed EAR to a similar degree at either 0° or 37°, whereas F(ab′)₂ fragments were inhibitory only at 37°. Taken together the results suggest that Fc receptors can be inhibited by antibodies with specificity against any cell surface antigen. The blocking mechanism may be due to steric hindrance by the Fc part of antibody molecules and/or F(ab′)₂ fragment mediated co-capping.

Association between immunoglobulin allotypes and immune responses to Haemophilus influenzae and Meningococcus polysaccharides

Serum samples were collected from 20 healthy White and 33 Black infants before and after immunisation with three doses of diphtheria-pertussis-tetanus vaccine and with one dose of Haemophilus influenzae type b polyribose phosphate vaccine and meningococcal group A and group C polysaccharide vaccines. Antibodies to these immunogens were measured and sera were allotyped for several Gm, A2m, and Km antigens. A highly significant association was found between the Km(1) allotype and the immune responses (difference between post-immunisation and pre-immunisation antibody levels) to H. influenzae and meningococcus C polysaccharides in the White children.

The possible role of isoantigens in protective immunity to malaria

The possibility that autoimmune responses to modified red cell antigens might be involved in protective immunity to malaria was investigated in Plasmodium berghei infection of August rats. Animals rendered anaemic by phenylhydrazine treatment at the time of immunization showed significantly greater protection than rats given antigen alone, or phenylhydrazine alone. Adoptive transfer experiments indicated that this enhanced response could be transferred with spleen cells.

Suppression of lymphoproliferative responses to alloantigens by autologous AML cells

Autologous acute myeloid leukaemia (AML), cells caused the suppression of incorporation of 3H-thymidine (3H-Tdr) by remission lymphocytes stimulated with allogeneic cells. In five patients, autologous AML cells suppressed 3H-Tdr uptake by lymphocytes stimulated with up to three different allogeneic cells. Responses to allogeneic AML cells were more strongly suppressed than responses to pooled allogeneic lymphocytes. Suppression was abolished by ultrasonic disintegration of the autologous AML cells, suggesting that a soluble factor was not involved. Suppression was absent from autologous AML cells exposed to ultraviolet light, or when untreated autologous AML cells were present in ratios of less than 1:1 to lymphocytes, or when added 24 or more hours after stimulation of remission lymphocytes with allogeneic cells. It is suggested that suppression is a property of the differentiative level of AML cells, rather than of their malignant properties, although malignant-transformation may bring AML cells into contact with circulating T cells in vivo. Autologous AML cells seem to interfere with the recognition phase of T cell function.

Immunochemical characterization of the Ly-8.2 murine lymphocyte alloantigen: possible relationship to actin

An immunochemical analysis of the Ly-8.2 antigen was performed. Reactivity of B10-radiolabeled T and B cell lysates with a C3H anti-AKR serum immunoprecipitates a major 43,000 m.w. protein detectable by one-dimensional gel electrophoresis. The protein can be radioiodinated, however, it does not appear to blind to lentil lectin. Two-dimensional gel electro phoresis and peptide-mapping studies indicate that this protein is structurally very similar to lymphocyte actin. The possible molecular relationship between Ly-8.2, other lymphocyte membrane antigens, and actin is discussed.